The present invention concerns an automatic control of a clutch in the drive train of a motor vehicle, having a transmission shifted by the driver between different transmission stages or gears and an engine controlled by the driver by means of a control element, for example a gas pedal. The clutch is automatically set by a motorized adjusting unit, actuated by the control, to a creeping torque at low travelling speed or when the vehicle is stationary and the transmission stage has been selected, the brake is unactuated and the control element is not actuated.
In motor vehicles with customary internal combustion engines, a transmission must be arranged in the drive train to allow the transmission ratio between the speed of the vehicle engine and the speed of the drive wheels to be changed according to the respective travelling speed and loading of the vehicle. In customary manually shifted transmissions, during the change of a transmission stage the power flow between engine and drive wheels has to be interrupted by releasing the clutch.
When starting the vehicle, the clutch must operate with slip, since the aforementioned transmission is not able to operate steplessly and conventional vehicle engines, in particular internal combustion engines, can only operate and deliver adequate power above a minimum speed.
It is known in principle to use automatic clutches for this purpose so that a clutch is automatically released when changing a transmission stage and is subsequently re-engaged. In starting situations, the clutch initially transmits only a limited torque, i.e. the creeping torque, which is adequate for making the vehicle start to slowly creep forward under normal driving conditions. If the vehicle is then accelerated by corresponding actuation of the gas pedal, the torque which can be transmitted by the clutch increases, so that, depending on the respective operating parameters, at a varying level of engine speed the clutch can transmit a torque which is above the engine torque.
It is known from EP 03 75 162 B1 to allow the automatic control of the clutch also to operate in dependence on the brake actuation in a creeping phase of the vehicle.